Informed consent is the cornerstone of ethical human subject research. The persistence of high expectations for therapeutic benefit reported by participants in early-phase oncology trials has been an on-going concern among researchers and ethicists. Early work on this issue focused on the possibility that patient-subjects have an inadequate understanding of the nature of the trials in which they participate. However, in recent years, researchers have begun to investigate a new possibility: the possibility that in reporting high expectations for benefit, patient-subjects are simply hoping for the best or expressing optimism. To date, researchers have not systematically investigated the extent to which this optimism reflects a bias (which social psychologists refer to as unrealistic optimism) that has the potential to distort the appreciation of risk/benefit information disclosed in the informed consent process. This proposal is an extension of a previously funded NCI-NIH study which gathered pilot data that suggested that unrealistic optimism was present among participants in early-phase oncology trials. The OBJECTIVES of this proposal are (1) to investigate the extent to which high expectations for therapeutic benefit in early-phase oncology trials reflect an optimistic bias; (2) to determine the specific factors that evoke the bias in this context; and (3)to determine the extent to which the bias impairs the appreciation of research-related risk/benefit information disclosed in the consent process. To accomplish these objectives, we will use four main instruments - the CRBA, the HPRF, The LOT-R, and the MacCAT-CR. The first two of these instruments have been widely used by social psychologists to assess unrealistic optimism in a range of populations. The third instrument has been widely used by social psychologists to distinguish unrealistic optimism from dispositional optimism and the fourth instrument has been used in previous research on the capacity to consent to clinical research. This proposal advances beyond our pilot study by recruiting a larger sample size with greater geographical and ethnic diversity, by seeking to distinguish unrealistic optimism from dispositional optimism, and by exploring whether unrealistic optimism predicts the decision to enroll in early- phase oncology trials. In addition, this proposal goes beyond the earlier research by testing for the impact of unrealistic optimism on the appreciation of risk/benefit information. Findings from our proposal will yield valuable insight into how social psychological biases, such as unrealistic optimism, impact informed consent and the decision to enroll in early-phase cancer trials. In addition, it will lay the groundwork for future efforts to develop an effective intervention for countering biases that may distort risk/benefit assessments among patients-subjects. In this way, the data obtained from this study have the potential to improve both the understanding and the practice of informed consent in human subject research.